The invention is drawn to the genetic modification of plants, particularly to the ablation of invertase inhibitor function to maintain female fertility.
In cereals, water deficits can disrupt reproductive development and induce large yield reductions. In fact, the shortage of water during pollination increases the frequence of kernel abortion in maize (Westgate and Boyer (1986) Crop Sci. 26:951). The effects of water deficit are also seen around anthesis which also affects grain number (Schussler and Westgate (1991) Crop Sci. 31:1196). The losses around anthesis have been variously attributed to abnormal embryo-sac development or decreased silk receptivity depending upon when the water deficit occurs.
Low water potential inhibits dry matter accumulation and increases the concentration of assimilates in reproductive tissues (Zinselmeier et al. (1995) Plant Physiol. 107:385). Leaf water potentials decrease as water deficits develop, and photosynthesis is inhibited at the low water potentials causing embryo abortion. It has been demonstrated that by infusing a modified tissue culture medium into the stems and maintaining the supply of carbohydrate in addition to amino acids, basal salts, plant growth regulators, vitamins, and myo-inositol, early reproductive development could be sustained (Boyle et al. (1991) Crop Sci. 31:1246).
Under conditions of adequate water, maize ovaries accumulate starch during pollination and early kernel growth. The partitioning into starch reserves depends on assimilate supply as well as demand. At low water potential, starch levels in the reproductive shoot decrease indicating that assimilate supply is not sufficient to meet demand in the reproductive tissues of water-deficient plants.
Sucrose is the predominate sugar in higher plants. It serves several important functions, including acting as the major carbohydrate transport form, as a storage compound, and as an osmoprotectant. Higher plants metabolize sucrose either by sucrose synthase or by invertases (Greiner et al. (1998) Plant Physiol. 116:733). Plant invertases are located in the vacuole, the cytoplasm, and the cell wall. These different invertase isoenzymes each have specific functions requiring independent regulation. Several invertase isoforms have been cloned and their expression studied with respect to developmental regulation and tissue or cell-preferred expression (Cheng et al (1996) Plant Cell 8:971; Weber et al. (1995) Plant Cell 7:1835).
Because stress can have deleterious effects on plant growth and yield, methods are needed to increase yield in plants, particularly under stress conditions.
Methods and compositions for increasing yield in plants, particularly seed plants, are provided. The compositions comprise novel nucleic acid molecules encoding invertase inhibitors, antisense nucleotides corresponding to invertase inhibitors, and variants and fragments thereof. Such compositions find use in methods to modulate invertase activity in plants. The compositions are also useful in methods to modulate kernel development and for protecting plants against the harmful/detrimental effects of stress and adverse environmental conditions. The nucleotide sequences may be provided in constructs for temporal, developmental, and tissue preference.
Transformed plants, plant cells, tissues, and seeds are additionally provided.